<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>let</title>
</head>
<body>
  <script>
    //声明变量
    let a
    let b, c, d
    let e = 100
    let f = 521, g = 'iloveyou', h = []

    //1. 变量不能重复声明
    // let star = '罗志祥'
    // let star = '小猪'

    //2. 块儿级作用域  全局, 函数, eval
    // if else while for
    // {
    //     let girl = '周扬青'
    // }
    // console.log(girl)

    //3. 不存在变量提升
    // console.log(song)
    // let song = '恋爱达人'

    //4. 不影响作用域链
    {
      let school = '尚硅谷'

      function fn () {
        console.log(school)
      }

      fn()
    }
  </script>
</body>
</html>